1. Field of the Invention
The present invention relates to dielectric pastes and manufacturing methods of plasma displays.
2. Description of the Related Art
In recent years, plasma displays have drawn attention as next generation large-sized displays, and hence techniques for reliably producing a highly fine plasma display at reasonable cost have been desired. Among members constituting plasma display mentioned above, one of quite high cost members is a back panel.
As shown in FIG. 1, the back panel is formed of at least electrodes 1, a dielectric layer 2, stripe shaped barrier ribs 3, and fluorescent layers 4 of R, G, and B, which are all formed on a substrate. In addition, recently, as shown in FIG. 2, grid shaped barrier ribs has also been frequently formed in which there are provided main barrier ribs 6 in a stripe shape and sub-barrier ribs 7 formed in the direction perpendicular thereto. In the back panel having any one of the barrier rib structures mentioned above, when a photosensitive paste method is used for forming electrode patterns and barrier rib patterns, it has become possible to reliably produce highly fine back panels; however, it has been still desired that the cost be further decreased.
Heretofore, in a process for manufacturing a back panel, steps of forming electrode patterns, a dielectric paste coating film, barrier rib patterns, and phosphor patterns have been performed, and materials used in the steps described above are separately fired after the respective steps (see FIG. 3). That is, in the process for manufacturing the back panel, at least four firing steps must be performed, and hence the productivity is low, resulting in an increase in cost. In addition, since a number of firing steps must be performed, a problem has occurred in that dimensional change of glass substrate is increased by repeated application of heat. Furthermore, when silver is used for forming electrodes, the silver migrates increasingly due to a number of firing steps, and hence this migration becomes partly responsible for a decrease in reliability of panels.
Accordingly, studies have been made on a simultaneous firing process for simultaneously firing some of the electrode patterns, dielectric paste coating film, barrier rib patterns, and phosphor patterns. For example, in Japanese Unexamined Patent Application Publication No. 11-7894, a simultaneous firing process has been disclosed in which, by increasing processing temperatures of inorganic powder used in electrodes, a dielectric layer, barrier ribs, and phosphors in that order, four members, that is, the electrodes patterns, dielectric paste coating film, barrier rib patterns, and phosphor patterns, are fired simultaneously. However, when the method described above is used, there have been serious two problems.
The first problem is that when the barrier rib patterns are formed by a photosensitive paste method or sand blast method, electrode lead wire portions 5, which are not covered with the dielectric paste coating film, of the electrode patterns are eroded by a developing solution for the barrier ribs or by polishing particles, and as a result, the electrode lead wire portions 5 are peeled off.
The second problem is that when the electrode patterns, dielectric paste coating film, and barrier rib patterns are simultaneously fired, large firing stresses are generated in both the electrode patterns and the barrier rib patterns in the direction so as to tear the dielectric layer, resulting in the generation of defects, such as disconnections of the electrode patterns or cracks formed in the dielectric layer.
In Japanese Unexamined Patent Application Publication No. 2001-26477, in the case in which two layers, i.e., the dielectric paste coating film and barrier rib patterns, are simultaneously fired, a manufacturing method has been disclosed in which the dielectric paste coating film is cured beforehand by heat so that cracks are not formed therein even when a firing stress is generated in the barrier rib in the simultaneous firing. However, in the case in which the electrode patterns, dielectric paste coating film, and barrier rib patterns are simultaneously fired, since a larger firing stress is generated, even when this manufacturing method is used, there has been a problem in that cracks are formed in the dielectric layer.